1. Field of the Invention
The present invention relates to telephone systems and related methods that enable a telephone in a private system to automatically access an external telephone line.
2. Description of the Prior Art
Many telephones systems are connected in a Centrex arrangement or on a private PBX. Such systems are often used by companies to interconnect office telephones or to interconnect telephones in different buildings. This enables one employee of the company to call another employee of that company without ever involving the local public telephone network. In such telephone systems, if a person wants to call a person outside of the Centrex arrangement or private PBX, then the telephone from which the call is being placed must first be connected to an external telephone line outside of that system. In order to connect a telephone to an external line, often a number sequence must first be dialed. For example, in many business telephone systems, though a user hears a dial tone when the telephone receiver is placed to the ear, that dial tone can only be used to dial other telephones contained within the same system. If a number outside the telephone system is dialed, the call will not be completed. It is common in many such telephone systems for a prefix code such as a number or a number sequence to first be dialed in order to reach an outside telephone line. In many systems, the number "9" must be dialed as the prefix code in order for a particular telephone to be connected to a dial tone for an outside line.
Many modern telephones display and store telephone numbers associated with incoming calls. In certain telephones, the number sequence of a prior incoming call can be retrieved from memory and can be automatically redialed. People can also purchase Caller ID.RTM. devices that store the number of incoming calls and redial those numbers on command. Such telephones and devices dial the exact number that was received. As a result, such telephones and devices do not work well in systems where prefix codes must be dialed in order to connect to an outside line. For example, suppose a telephone in a system receives a call from New Jersey from the number (908) 321-4567. The telephone stores the number sequence "9083214567" in its memory. If that number is retrieved to be automatically redialed, the exact number sequence 9083214567 will be redialed. If the telephone is in a system where "9" must first be dialed to reach an outside line, the following results. When the "9" is redialed, the telephone connects to an outside line. When the next numbers "0832" are redialed, the local telephone network receives the "0" and assumes that the person is placing either an operated assisted call or a calling card call to area code "832". The next three numbers "145" are dialed as the exchange and the last two numbers are dialed as an incomplete final call address. So instead of dialing the number 321-4567 in area code (908) as was intended, the telephone dials the incomplete number 145-67 in area code (832).
In the prior art, telephones used in Centrex arrangements or on private PBXs have solved this problem by various program functions that enable a user to program the needed dialing prefixes into a telephone. However, many telephones do not have alpha-numeric displays that can prompt a user. As a result, a user must read the telephone manual that came with the telephone and that user must perform the proper programming sequence. Since most people move into offices where the telephone is already in place, the manuals for the telephone are seldom available and the proper programming sequence rarely executed. Rather, the user of the telephone simply ignores the call redial function present in the telephone.
A need therefore exists for a telephone and associated method that can be used in a system having a private PBX enabling the call redial functions of that telephone to operated properly.